The present invention relates to a cylinder/piston unit with a cylinder and with a piston which is guided therein and is sealed off in a sterile manner by a rubber seal, the cylinder and the piston enclosing a chamber that can be filled at least temporarily with active substance, and the cylinder having at least one discharge element at its front end.
In the case of medicament chambers or syringes that are stored in a filled state and that are closed off in a sterile manner by means of a piston among other things, the piston coming into contact with the injection solution is made of rubber or has at least a rubber seal. Since such a piston that provides sterile sealing has a high degree of static friction and kinetic friction relative to the glass cylinder or plastic cylinder, the piston according to DIN 13098, part 1, is lubricated with polydimethylsiloxane, for example. Consequently, the lubricant is also administered along with the injection solution.
Another alternative is to seal the medicament chamber or syringe barrel (see DE 10 2005 054 600). In the latter document, the pistons do not have any rubber seals. Here, for example, the rear face of a medicament chamber is heat-sealed with a film or is closed off in a sterile manner by a spray-on varnish.
The object of the present invention is therefore to develop a cylinder/piston unit which can be pre-filled and in which, despite a sterile sealing of the piston, only a slight force has to be applied in order to accelerate and/or move the piston.